Carburetor



Sept. 25, 1934. M PRENTISS 1,974,586

CARBURETGR Filed Feb. 1, 1932 2 Sheets-Sheet 2 INVEN TOR. @z/ausr/NMPEf/VT/JS Q. fi Q11:

ATTORNEY Patented Sept. 25, i 1934 PATENT OFFICE CARBURETOR Augustin M.Prentiss, San Antonio, Tex., assignor to Bendix Aviation Corporation,South Bend,

Ind., a corporation of Delaware Application February 1, 1932, Serial No.590,295

-1 Claim. (01.123-122) This invention pertains to carburetors and moreparticularly has reference to means for maintaining the temperature ofthe carburetor and fuel-air mixture within desired limits, irrespectiveof wide variations in the temperature of the engine and the airsurrounding the car-.- buretor.

I It has long been known in the carburetor art that best results areobtained when the fuel-air mixture supplied to the engine is betweencertain optimum temperature limits and that variations above or belowthese limits result not only in a marked decrease in power andefliciency but also in other operating difiiculties such as vapor. locksand irregular firing of the engine. The best results are obtained whenthe fuel-air mixture is between ordinary summer temperature and theboiling point of the lightest fraction of hydrocarbon in the liquidfuel. If the temperature of the fuel-air mixture falls much below normalsummer temperature volatilization of the liquid fuel is retarded,whereas if 'the temperature exceeds the boiling point of its lightestfraction, the liquid fuel begins to boil, giving rise to vapor locks inthe liquid fuel supply line and also misfires of the engine, whenever avapor bubble passes through the main fuel nozzle.

\Heretofore the problem has been to maintain the fuel-air mixture withinthe optimum temperature limits indicated under actual operatingconditions 'where the temperature of the carburetor and the airsurrounding the carburetor may vary all the way from'20 degrees to 30degrees below zero Fahrenheit to 150 degrees above zero Fahrenheit.

Due to the large amount of heat radiated by an internal combustionengine, notwithstanding that it may be cooled by a water jacket, and theheat throw-ofi by the radiator, the temperature under the hood of anautomobile is always much higher than the atmosphere outside the hood,both in winter and summer. carburetor has always been exposed not onlyto the heated air under the hood butalso to additional heat transmittedby conduction through the intake manifold from the engine to thecarburetor. This latter heat raises the temperature of the carburetorconsiderably above the air surrounding it, so that often in hot summerweather the temperature of the carburetor is materially above theboiling point of a part of the liquid fuel and unsatisfactory operationresults.-

Also in cold winter weather, the temperature of the carburetor,notwithstanding the sources of heat indicated above, is often far belowefficient Heretofore, the,

vaporization temperature and loss of power and efliciency occurs.

While it has formerly been proposed to heat the carburetor in coldweather by circulating the exhaust gases or hot water from the engine ina jacket surrounding the carburetor, and to arrange a manuallycontrolled valve so that the amount of such heating fluid may beregulated, so far as I am aware, it has never been proposed to cool thecarburetor in hot weather by circulating cold water in a water jacketaround the carburetor so arranged as to completely insulate thecarburetor from the heated air under the hood and thus maintain thetemperature of the carburetor not only below the temperature of theheated air under the hood but also of the outside atmosphere, wheneverthese temperatures exceed the optimum temperature of i the fuel-airmixture. i

It has also, so far as I am aware, never been proposed to maintain thecarburetor and fuel-air mixture between certain desired limits oftemperature, necessary for best operating results, by circulating bothwarming and cooling fluids around the carburetor and automaticallycontrolling -the circulating of these fluids so as to maintain thecarburetor and fuel-air mixture within the desired temperaturerangeregardless of the temperature of the atmosphere.

An object of this invention is to. provide a carburetor with means forautomatically controlling its temperature, and the temperature of thefuelair mixture,-within certain desired operating limits, regardless ofthe temperature of the atmosphere.

Another object of this invention is to insulate the carburetor from theheated air under the hood by circulating a cooling medium in a jacketcompletely enveloping the carburetor, so that the temperature of thecarburetor and the fuelair mixture will not exceed the boiling point ofthe lightest fraction of the liquid fuel.

Still another object of my invention is to provide means forautomatically controlling, within certain limits, the temperature of theair entering the carburetor so as to obtain in hot weather air coolerthan that under the hood and in cold weather warmer than that under thehood.

With these and other objects in view which may be incident to myimprovements, my invention consists in the combination and arrangetom ofthe hood space.

of an automobile in which are located a conventional water-cooledinternal combustion engine.

and radiator, in operative connection with a carburetor embodying myimprovements.

Figure 2 shows in central longitudinal section, on an enlarged scale,the carburetor shown in Figure 1;

Figure 3 shows a front elevation of the same partly in section along theline 33 of Figure 2.

Figure 4'is an enlarged, vertical section of thermostat valve shown inFigure 1.

Referring to the drawings and particularly to Figure 1, the referencenumeral 1 denotes the hood and 2, the dashboard, of an automobile havinga multicylinder internal combustion engine 3 which is located within thehood 1 and cooled by a radiator 4 and fan 5 inthe usual way. The hotwater manifold 6 is connected to the top of the radiator 4 by a pipe '7in'which is located a valve 8 controlled by a thermostat 9 in theradiator, as clearly shown in Figure 1. The function of valve 8 is toprevent circulation of water from the engine to the radiator until thetemperature of the water reaches a certain point sufficient to operatethe thermostat 9 and open valve 8. This hastens the warming up of theengine. The same results may also be obtained by providingthermostaticallyoperated shutters in front of the radiator cutting offthe circulation of air therethrough until the temperature of the waterin manifold 6 is sufliciently highto operate the thermostat actuatingthe shutters. These are conventional features associated with myinvention but forming no part thereof.

The bottom of the radiator 4 is connected to the bottom of the waterjacket surrounding the cylinders of the engine by a pipe 10 having ableed pet cock 11 and circulating pump 12 connected thereto. Below pipe10-, radiator 4 has a separate section 4a having a pipe 10a andcirculating pump 12a connected thereto, for cooling the carburetor ashereinafter described.

The reference numeral 13 denotes the carburetor as a whole, connected inthe usual manner to the riser 14 of the intake manifold (not shown) andto an air cleaner 15. While I have shown an updraft carburetor in thedrawings, it will be apparent from the description hereinafter that myinvention is equally applicable to downdraft carburetors and to pressurefeed carburetors as well as suction feed types. The intake pipe 16 ofthe air cleaner extends downward-1y below the pan 17 of the automobilewhich encloses the bot- Intake pipe 16 is connected by a pipe 18 to anair heater or stove 20 surrounding the exhaust manifold 21 of the enginein the conventional manner. At the junction of pipes 16 and 18, a flapvalve 22 is so arranged as to alternately cut off the entrance of air tothe air cleaner through either pipe 16 or 18 or toregulate theproportion of air entering through each pipe. In this way thetemperature of the air entering the carburetor is regulated. Since theoutside air under the pan is cooler than the heated air under the hood,valve 22 closes pipe 18 in hot weather and permits air to enter onlythrough pipe 16. Conversely, in cold weather, when heated air isdesired, valve 22 closes pipe 16 and permits. air to enter only throughpipe 18 which connects with heater 20. In moderate weather valve 22would have an intermediate position, as shown in Figure 1 permitting amixture of cool air through pipe 16 and hot air'through pipe 18. It isobvious that valve 22 thus controls, within the limits of thetemperature of the outside air on the one hand and the temperature ofthe stove 20 on the other, the

"temperature of the air entering the carburetor.

The operating mechanism of valve 22 will be hereinafter described.

The carburetor 13 is provided with an integral water jacket 23 whichcompletely surrounds and envelops the body of the carburetor, includingthe fuel reservoir, as clearly shown in Figure 2. This water jacket 23is connected by a pipe 24 to the pump 12a on its high pressure side, andby a pipe 25 to the radiator 4a. Pipe 25 is also connected to pipe 10 onthe low pressure side of pump 12 and is provided with a two-waythermostat valve 25a which is adapted to open communication be-' tweenpipes 25 and 10, and close communication through pipe 25 to the radiator4a, in cold weather, and to close communication between pipes 25 and 10and open communication through pipe 25 with radiator 4a in hot weather,as clearly shown in Figure 1, for a purpose to be more fully explainedhereinafter.

Referring now to Figure 2, the reference numeral 2'7 denotes the body ofa carburetor having an air intake 28, a Venturi throat 29, a mixingchamber 30 and mixture outlet 31 controlled by a throttle valve 32 inthe usual manner. A main liquid fuel nozzle 33 communicates through apassageway 34 and port 35 with an integral liquid fuel reservoir 36. Aneedle valve 37 controls the flow of liquid fuel through port 35 fromreservoir 36 to nozzle 33.

Reservoir 36 is supplied with liquid fuel through inlet 38 and pipe 39by a liquid fuel pump (not shown). A valve 40, actuated by float 41,maintains the liquid in reservoir 36 at a constant level. A vacuumcontrolled acceleration pump 42 opens an auxiliary port 43 in the bottomwall of reservoir 36 and supplies additional fuel as required foracceleration, as clearly shown in Figure 2. The slow speed or idle fuelfeed is supplied through a plurality of ports 44 which bestride thethrottle 32 (in closed position) and are connected by a passageway 45with fuel nozzle 33.

Reservoir 36 is closed by a cover 46 held in place by a plurality ofscrews 47 and sealed by a gasket 48. Cover 46 is also provided with awater jacket 49 which is connected to water jacket 23 by a plurality ofpassages 50 as shown in Figure 2. The mechanism controlling thetemperature of the water circulating in jackets 23 and 49 is containedin a housing 51 which is cast integral with carburetor body 27 and isclosed by a cover plate 52, as shown in Figure 2. Integral with plate 52is a circular valve housing 53 which encloses a valve 54 as shown inFigures-2 and 3. Valve 54 is fixed to a shaft 55 which is journalled inthe body of the carburetor 27 and inplate 52. Near its inner end shaft55 carries a spiral thermostat 56 which is coiled around shaft 55 andattached at its inner end to said shaft by a plurality of screws 57. Atits outer end coil 56,is attached by a pin 58 to the body of thecarburetor 27 as clearly shown in Figure 2. The thermostat coil 56, thusmounted is enclosed by a chamber 59 forming part of the jacket 23 andcommunicating therewith through ports 60. The coil 56 is thus immersedat all times in the water circulating through jacket 23, and is subjectto the temperature of this water.

When the temperature of the water rises, coil 56 expands, unwinds, andmoves valve 54 in a clockwise direction to the position shown in fulllines in Figure 3, whereupon communication is established between coldwater supply pipe 24 and jacket 23 through ports 61 and 62 in valvehousing 53. Conversely, when the temperature of the water circulatingthrough jacket 23 falls, coil 56 contracts, winds up, and moves valve 54in a counterclockwise direction to the position shown in dotted lines inFigure 3, whereupon communication between cold water pipe 24 and jacket23 is cut olf and hot water enters jacket 23 from pipe 26 through ports64, 62 and 63. It will also be noted fromFigure 3 that when valve 54 isin the position shown in full lines, permitting the circulation of coldwater around the carburetor, the hot water entering from pipe 26 isdischarged directly out through port 65 in valve housing 53, and pipe 25to pipe 10 on the low pressure side of pump 12, and conversely whenvalve 54 is in the position shown in dotted lines, permittingthecirculation of hot water around the carburetor, the cold water frompipe 24 is discharged directly out through port 65 and pipe 25 in thesame manner.

Since valve 54 is thinner than the width of ports 62 and 65, when valve54 is in a vertical position, midway between the positions shown inFigure 3, both hot and cold water will enter housing 53 and willdischarge through ports 62 and 63 into jacket 23 where they willcommingle and result in water having a medium or intermediatetemperature. In this way, the temperature of the water circulatingaround the carburetor is regulated and controlled by valve 54 which isin turn actuated by thermostat 56 responsive to the temperature of thecarburetor.

Shaft 55 carries fixed to its outer end an arm 66 which is connected byan adjustable link 67 to an arm 68 on air valve 22, so that as valve 54is moved by thermostat 56 in a clockwise direction, valve 22 is raisedso as to restrict pipe 18 and open pipe 16 and, conversely, when valve54 is moved in a counterclockwise direction, valve 22 is lowered to cutoff pipe 16 and open pipe 18.

' In this way, the temperature of the air entering the carburetor iscontrolled and made to vary directly and proportionately with thetemperature of the water circulating around the carburetor. Since thewater jackets 23 and 49 surround and completely insulate the floatreservoir 36, the temperature of the liquid fuel in the float reservoiris sensibly that of the water in jackets '23 and 49, since the capacityof reservoir 36 is made sufficient to insure an adequate period of timeduring which the liquid fuel remains in the reservoir in contact withthe walls of jacket 23.

The operation of my device is as follows. In cold weather, when theengine is first started, the engine, carburetor and water in bothcooling systems are all at the temperature of the atmosphere, valve 8 isclosed and valve 25a cuts off radiator 4a and opens communicationbetween pipes 25 and 10. The first explosions in the cylinders of theengine quickly heat the water in manifold 6 which is held therein andprevented from circulating to the radiator by valve 8. Part of this hotwater travels down pipe 26 and since valve 54 is in its cold (dotted)position, it circulates around the carburetor and is discharged outthrough pipes 25 and 10 to the low pressure side of the pump 12. As pump12 runs continuously whenever the engine is running, it creates a higherpressure in manifold 6 than exists in pipe 10 between the radiator 4 andthe pump, and thus causes a vigorous circulation of hot water around thecarburetor. Since the superior pressure in manifold 6 is greater whenvalve 8 is closed than when it is open and the water is circulatingthrough the radiator, it follows that the most vigorous circulation ofhot water takes place when the engine is first started in cold weather,which is as desired because the carburetor then requires the most heat.After valve 8opens, the same circulation continues around the carburetorbut in a lessened degree. The temperature of the water in the enginecooling system is largely determined in cold weather by the adjustmentof thermostat 9 or the shutters on the radiator if such are used, andcan be regulated as desired. However, the water in manifold 6 is alwaysappreciably hotter than that in any other part of the engine coolingsystem.

When the engine has been operating a sufficient time to bring the waterin its circulating system to a uniform temperature the carburetor isalso at its optimum temperature. While the carburetor is thus maintainedat its optimum temperature, the air entering the carburetor is alsobrought up to the same temperature by stove 20 and hence the fuel-airmixture delivered by the carburetor to the engine is at substantiallythe same temperature, regardless of the temperature of the atmosphere.Thermostat 56 may be calibrated to maintain any desired constanttemperature near that of the carburetor temperature in winter, whichgives optimum operatingresults.

In hot weather, when the engine is started, the engine, carburetor andwater in both cooling systems are also at the temperature of theatmosphere. Valve 25a opens communication with radiator 4a and cuts 01fcommunication between pipes 25 and 10, and the water in the carburetorcooling system is free to circulate through the radiator 4a where it iscooled below atmospheric temperature by radiation losses. 1

Cold water from pipe 10a travels up pipe 2 under the pressure created bypump 12a and since valve 54 is in its warm (full line) position, itcirculates around the carburetor and is returned through pipe 25 back toradiator 4a and pipe 10a to the low pressure side of the pump. Sincethere is a great difference in temperature between the water in jacket23 and that in radiator 4a, circu-. lation will also be caused byconvection and pump 12a might be omitted. By this continuous circulationof cold water, the carburetor is maintained at a temperature far belowengine temperature and much cooler than the heated air under the hood towhich the carburetor has been heretofore exposed. At the same time, theair entering the carburetor is taken from under the pan and is atatmospheric temperature which again is much less than that of the heatedair under the hood. As the liquid fuel in reservoir 36 is also cooled bythe circulation of water around the carburetor, it is maintained at atemperature lower than the boiling point of its lightest fraction and inthis way vapor locks and misfires due to vapor bubbles are prevented. Inorder to prevent heating of the liquid fuel before it enters reservoir36, the portion of pipe 39 exposed to the air under the hood should bereduced to a minimum and the fuel pump either located below the pan 17or provided with a water jacket connected in series with the carburetorwater jacket.

I have found by the means described above that, notwithstanding theheated air under the hood, and the heat transmitted by conduction fromthe engine through the intake manifold to the carburetor, the carburetorcan be maintained at an I claim:

In an automobile, an internal combustion engine, a carburetoroperatively connected thereto, separate liquid cooling systems connectedto said engine and carburetor respectively, and means for selectivelyheating said carburetor from said engine cooling system or cooling saidcarburetor from its separate cooling system depending upon thetemperature of said carburetor.

- AUGUSTIN M. PRENTISS.

